The invention is based on a traction drive for driving and for performing regenerative braking of a rail vehicle or of a combination of rail vehicles, wherein at least one permanently excited synchronous motor and one traction current converter are assigned to at least one axle of the rail vehicle or of the combination of rail vehicles, and wherein the traction current converter has at least one machine-side pulse current converter, and the permanently excited synchronous motor is connected at its terminals to a changeover switch in such a way that the permanently excited synchronous motor can be connected to the pulse current converter to perform driving or to a load circuit containing a load to perform regenerative braking. The invention is also based on a device for correcting loads during the regenerative braking of rail vehicles or combinations of rail vehicles containing an air spring device with at least one air spring bellows, by means of a traction drive.
The objective when equipping rail vehicles is to use ever more effective and lightweight drive machines. Conventionally, inverter-fed asynchronous machines are used as the standard drive machine. However, these machines offer little potential for further development in terms of reducing their mass and torque density; when used in rail vehicles such machines usually require a transmission. Accordingly, increasing efforts are currently being made to develop and use permanently excited synchronous machines as vehicle drives.
By virtue of its high torque density, this type of machine permits direct drives to be implemented and particularly the elimination of the transmission means that it allows the mass of the drive train to be reduced to a very high degree.
Permanently excited synchronous machines have a number of unique features compared to asynchronous technology owing to their permanent excitation. Therefore, it is possible, for example, in the case of a rotating machine, to achieve a braking effect in addition to the inverter-regulated generator mode using purely passive components. The braking effect achieved by a permanently excited synchronous machine by connecting braking resistors is known from DE 101 60 612, which defines the generic type.
When the rotating, permanently excited synchronous machine with braking resistors is connected into the circuit, a characteristic torque curve or characteristic force curve (also referred to herein as a natural braking characteristic curve) is obtained as a function of the rotational speed of the synchronous motor and, therefore, also of the speed of the vehicle. This braking characteristic curve has a profile maximum value when plotted against the rotational speed/speed.